Build solar systems using their planets (or other players' planets) and adjust their orbital parameters. For example, they could easily make a solar system with an Earth-like planet orbiting a gas giant.

Universe Sandbox 2 saves .ubox files, which are PK-zip archives containing other files, in particular simulation.json that describes all of the bodies and their parameters.

I think US2 is the perfect editor to work out the orbital parameters for a realistic solar system. However, SR2 might have to impose constraints on what sort of simulations it can import, because US2 allows a lot of bonkers scenarios.

@AndrewGarrison Is there any possibility for detail brushes? Like, I want to mold my own mountains and paint the cliffs. Is that a thing yet? Or could it be?
And will there be a grass or tree tool that could perhaps host other 3D objects?